Scientists who had warned that Hispaniola risked a major earthquake have returned to Haiti this week to collect data on the chances of it happening again.

This month's (12 January) magnitude 7 earthquake was caused by the rupture of the Enriquillo fault, which runs along the southern side of Hispaniola — made up of Haiti and the Dominican Republic — to Jamaica.

Eric Calais, a geophysicist from the University of Purdue in the United States and leader of the research team, told SciDev.Net that the data collection must be done quickly.

The geological information will soon disappear and information about the fault rupture is crucial to validate further calculations of what could happen next, he said.

Calais' team has been working in the area for five years, using GPS (global positioning system) markers to measure the movement of the fault with precision. The scientists intend to find and map the ruptured area of the fault, resurvey existing GPS markers, and install ten new markers to monitor the changes that will occur as the Earth's crust readjusts.

The Enriquillo fault "has the historically bad habit of repeating earthquakes, so we want to try to understand it further", he said.

During the 18th Caribbean Geological Conference — held in 2008 in the Dominican Republic — Calais was part of a group of scientists that presented a study predicting a major earthquake that, they said, should be considered "high priority" for the Dominican Republic, Haiti and Jamaica.

The last major earthquake, in south-central Dominican Republic, had been in 1751 and that, combined with the rate at which tectonic plates were moving against each other, led the scientists to predict that there were two metres of strain on the fault — enough to generate a magnitude 7.2 earthquake.

The team met with the Haitian authorities to discuss the risk and the government attempted to put together a risk-reduction plan but limited action was taken, said Calais.

Even though most scientists agree that a 7 magnitude earthquake is not very large, January's event killed an estimated 200,000 people and left capital city Port-au-Prince practically in ruins.

Calais said this was because the earthquake was shallow and because the city is densely populated with poor infrastructure — and sits right on the fault.

The earthquake may even have increased the risk of another in the future. A team from the United States Geological Survey has found that stress on other areas of the Enriquillo fault near Port-au-Prince has increased since this month's disaster.

Source: SciDev Net
Date: 28 January, 2010